Compared with liquid crystal displays, organic light-emitting display devices have many advantages, such as self luminescence, all solid state, wide angle of view, fast response and so on, the organic light-emitting display devices are considered to have a great application prospect in the field of display and have been widely used in mobile phones, digital cameras, personal digital assistants (PDA) and notebook computers.
Each of the organic light-emitting display devices includes a plurality of pixel units, and each of the pixel units comprises a switching transistor, a driving transistor and an organic light-emitting diode (OLED). The OLED is a current mode light-emitting device, which mainly includes anode, cathode and organic material functional layer. A main work principle of the OLED is that carriers driven by electric field formed by the anode and the cathode are injected into the organic material functional layer and recombine in the organic material functional layer to emit light.